Re: [PATCH 05/15] irq: add generic_handle_arch_irq()

From: Mark Rutland <mark.rutland@arm.com>
To: Guo Ren <guoren@kernel.org>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Vincent Chen <deanbo422@gmail.com>,
	Greentime Hu <green.hu@gmail.com>,
	Jonas Bonn <jonas@southpole.se>,
	kernelfans@gmail.com,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Russell King <linux@armlinux.org.uk>,
	Marc Zyngier <maz@kernel.org>, Nick Hu <nickhu@andestech.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Paul McKenney <paulmck@kernel.org>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Stafford Horne <shorne@gmail.com>,
	Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>,
	Thomas Gleixner <tglx@linutronix.de>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	vgupta@kernel.org, Will Deacon <will@kernel.org>
Subject: Re: [PATCH 05/15] irq: add generic_handle_arch_irq()
Date: Fri, 22 Oct 2021 09:52:02 +0100	[thread overview]
Message-ID: <YXJ7YzZoJ1ZkLl4X@FVFF77S0Q05N> (raw)
In-Reply-To: <CAJF2gTShTh5be3SxaVwAzbXTb=LZi-qfweXBvyLeg9TyKgfLNg@mail.gmail.com>

On Fri, Oct 22, 2021 at 10:33:53AM +0800, Guo Ren wrote:
> On Fri, Oct 22, 2021 at 2:03 AM Mark Rutland <mark.rutland@arm.com> wrote:
> >
> > Several architectures select GENERIC_IRQ_MULTI_HANDLER and branch to
> > handle_arch_irq() without performing any entry accounting.
> >
> > Add a generic wrapper to handle the commoon irqentry work when invoking

Ah, I'd typo'd 'common' there; I'll go fix that...

> > handle_arch_irq(). Where an architecture needs to perform some entry
> > accounting itself, it will need to invoke handle_arch_irq() itself.
> >
> > In subsequent patches it will become the responsibilty of the entry code
> > to set the irq regs when entering an IRQ (rather than deferring this to
> > an irqchip handler), so generic_handle_arch_irq() is made to set the irq
> > regs now. This can be redundant in some cases, but is never harmful as
> > saving/restoring the old regs nests safely.
> Shall we remove old_regs save/restore in handle_domain_irq? It's duplicated.

We do, in patch 15 when handle_domain_irq() is removed entirely. :)

Removing it immediately in this patch would require more ifdeffery and/or
another copy of handle_domain_irq(), and since the duplication doesn't cause a
functional problem, I think it's better to live with the temporary duplication
for the next few patches than to try to optimize the intermediate steps at the
cost of legibility.

Thanks,
Mark.

> > Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> > Cc: Marc Zyngier <maz@kernel.org>
> > Cc: Thomas Gleixner <tglx@linutronix.de>
> > ---
> >  kernel/irq/handle.c | 18 ++++++++++++++++++
> >  1 file changed, 18 insertions(+)
> >
> > diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c
> > index 221d80c31e94..27182003b879 100644
> > --- a/kernel/irq/handle.c
> > +++ b/kernel/irq/handle.c
> > @@ -14,6 +14,8 @@
> >  #include <linux/interrupt.h>
> >  #include <linux/kernel_stat.h>
> >
> > +#include <asm/irq_regs.h>
> > +
> >  #include <trace/events/irq.h>
> >
> >  #include "internals.h"
> > @@ -226,4 +228,20 @@ int __init set_handle_irq(void (*handle_irq)(struct pt_regs *))
> >         handle_arch_irq = handle_irq;
> >         return 0;
> >  }
> > +
> > +/**
> > + * generic_handle_arch_irq - root irq handler for architectures which do no
> > + *                           entry accounting themselves
> > + * @regs:      Register file coming from the low-level handling code
> > + */
> > +asmlinkage void noinstr generic_handle_arch_irq(struct pt_regs *regs)
> > +{
> > +       struct pt_regs *old_regs;
> > +
> > +       irq_enter();
> > +       old_regs = set_irq_regs(regs);
> > +       handle_arch_irq(regs);
> > +       set_irq_regs(old_regs);
> > +       irq_exit();
> > +}
> >  #endif
> > --
> > 2.11.0
> >
> 
> 
> -- 
> Best Regards
>  Guo Ren
> 
> ML: https://lore.kernel.org/linux-csky/